Polymer blends of amino-formaldehyde prepolymers and divalent metal salts of dibasic organic acids

ABSTRACT

METAL SALTS OF ALKANEDIOIC AND AROMATIC DIBASIC ACIDS ARE USED TO IMPROVE ONE OR MORE OF THE PHYSICAL PROPERTIES OF CERTAIN THERMOPLASTIC AND THERMOSETTING RESINS, EITHER BEFORE OR AFTER EXPOSURE TO HIGH TEMPERATURES.

United States Patent US. Cl. 260-616 6 Claims ABSTRACT OF THE DISCLOSURE Metal salts of alkanedioic and aromatic dibasic acids are used to improve one or more of the physical properties of certain thermoplastic and thermosetting resins, either before or after exposure to high temperatures.

This is a division of application Ser. No. 353,266, filed Mar. 19, 1964 now US. Pat. No. 3,418,273.

The invention herein relates to polymer blends derived from divalent metal salts of dibasic organic acids, to mixtures useful in the production of these blends and to processes for their production.

organometallic salts have been used in a wide variety of polymer compositions, e.g., as fillers, colorants, opaque agents, dulling agents, inhibitors, polymerization catalysts, light stabilizers, etc. The organometallic salts of this invention are used to improve one or more of the physical properties of several classes of polymers, for the most part of the strength thereof, either initial or after exposure to high temperatures. However, the property which is improved and the extent thereof depends upon the class of polymer involved, each class benefiting uniquely. For example, with the phenol-formaldehyde novolaks, a marked improvement in tensile strength is obtained whereas with cellulosic ethers significant increase in elongation is the most marked improvement obtained. Because the organometallic salts employed in the polymeric compositions described herein have an effect which differs unpredictably from polymer class to polymer class, each class will be dealt with individually hereinafter.

The polymers employed in the novel compositions fall generally into two broad classifications, i.e., thermosetting resins or plastics including the phenolics, ureas, melamines and polyesters, and the thermoplastic resins, including polystyrenes, polyacrylates and cellulose ethers and esters. The elastomers, e.g., natural rubbers, polybutadienes, silicones, linear polyurethanes, are not resins or polymers within the meaning of the terms as used herein. Polyvinylidene chlorides, polyvinyl chlorides and like plasticized polymers are also not within the scope of this invention.

The organometallic metal salts employed in the novel compositions described hereinafter are divalent metal salts of dibasic organic acids selected from the group consisting of alkanedioic and aromatic carbocyclic dibasic acids. The metal cation portion is preferably those of the Group II metals of the Periodic Table, desirably of an atomic number from 1256, inclusive, and desirably also of the Group II-A. Calcium is the metal of choice. The dibasic acids preferably contain from 4 to 12 carbon atoms, more preferably from 6 to 10.

The saturated alkanedioic acids are preferably of 6 to 12 carbon atoms, e.g., of the formula HOOC (CH ),,-COOH in which n is 6 to 12. The aromatic carbocyclic dibasic acids are preferably of 6 to 12 carbon atoms and are preferably disulfonic or dicarboxylic acids. Especially preferred are sebacic acid and the phthalic acids. Calcium sebacate, calcium phthalate, calcium isophthalate and calcium terephthalate, are the organometallic salts of choice with calcium phthalate preferred over all others.

A simple divalent metal salt of a dibasic organic acid can be employed or a mixture of such salts, improved results being sometimes obtained with such mixtures. The salts are employed in amounts from about 2 percent to about 25 percent, preferably about 5 to about 20 percent, e.g., 5 to 15 percent, calculated on the weight of the organic polymer or prepolymer employed. The optimum and minimum and maximum amounts will vary from polymer to polymer. As a general rule, however, amounts below 2 percent have relatively little effect and amounts above 25 percent have little favorable effect and produce adverse effects as the percentage is increased. About 5 to 10 percent is usually the amount of choice.

These organometallic salts can be formed in situ when the polymer blend is formed by milling or by polymerization at elevated temperatures, e.g., above about C. and more preferably about C. or above, by the use of a mixture of an anhydride or acid and a hydroxide or oxide of the metal in amounts which will react at elevated temperatures to form the desired amount of the selected organometallic salt, e.g., a mixture of phthalic anhydride and calcium oxide.

The examples set forth hereinafter are illustrative only and are not to be construed as limiting the inventions.

(A) PHENOL-FORMALDEHYDE POLYMERS According to this invention, a polymerizable composition is provided comprising a phenolic prepolymer and from about 2 to about 25 percent by weight thereof of a divalent metal salt of a dibasic organic acid as described above. These compositions are polymerized by the process of this invention to form novel resite and cured novolak polymeric compositions having improved thermal stability and other enhanced properties useful in phenolic polymers.

Four basic improvements in physical properties have been observed when an organometallic salt as described herein is incorporated into the mix used to form the phenolic resin, i.e., improved thermal stability, tensile strength, and improved resistance to water and aging. Such improvements allow considerable flexibility in solving such additional problems as case of processing and dimensional stability. For example, because of the increased strength from use of the herein described metal salts, a lower strength phenolic with a higher flow can be used. This leads to a process improvement by increasing flow rate in the mold. Similarly, this improved strength allows the use of shorter asbestos fibers in reinforced phenolics leading to better processability and use of a lower cost fiber.

The improvement in water resistance results in improved dimensional stability and surface properties such as electricals, etc.

The improvement in thermal stability and aging extends the usefulness of phenolic resins into higher temperature applications. Thus, such modified phenolics find use at temperatures 5075 C. above the present temperature limitations for phenolics.

The phenolic prepolymers of the polymerizable compositions of this invention include novolaks, preferably unmodified, resitols and resoles.

Novolaks are acid catalyzed phenol resins having a phenol/formaldehyde ratio greater than 1, exhibiting very little, if any, cross-linking and are permanently fusible and soluble. Their mean molecular weight is usually less than 1,000. They can react under alkaline conditions, heat and pressure to form methylol groups which then yield resite type products.

Resoles are A-stage alkaline catalyzed resins soluble in alkalies, alcohols, ketones and to some extent Water. They have a high hydroxy content and a relatively low molecular weight.

Although preferably unmodified, the phenolic prepolymers can be modified with the conventional modifies, e.g., chromium oxide.

These phenolics are preferably phenol-formaldehyde polymers although cresol or part cresol and other alkyl phenols and other aromatic hydroxy compounds can be used as the precursor as well as most active aldehydes, e.g., acetaldehyde, glyoxal and furfural.

The polymerizable compositions of this invention can include modifying agents, e.g., glycerol, fatty acids and alkyd resins, and fillers and extenders, e.g., wood flour, walnut-shell flour, asbestos, cellulosic or glass fibers, rubber, carbon, mica, oxides, silicates and carbonates, including zinc oxide, barium oxide, calcium oxide, titanium oxide, zinc oxide, calcium carbonate, diatomite, alumina, silicon carbide, barium sulfate, etc. Because the property enhanced the most is thermal stability, the heat resistant extenders and fillers conventionally employed in high temperature phenolics are the fillers of choice. Articles reinforced with glass, asbestos, paper or cotton cloth, mats or sheets or fibers employing a polymerizable composition of this invention are especially preferred embodiments of this invention.

The preferred cured articles of this invention are formed from about -80 parts by weight of phenolic resin, about 1-15 parts by weight of organometallic salt and about 94-5 parts by Weight of filler, preferably to 60 of the resin, 1 to 10 of the salt and 89 to 30 of filler.

The usual curing techniques and procedures are employed in the process of this invention. Both wet and dry formed phenolic prepolymers can be employed. Usually the prepolymer is employed as a finely ground powder. As with conventional phenolic resins, fine particle size and thorough mixing of ingredients are desirable.

The novel polymerizable compositions can be used to form laminates, compression cast and transfer molded articles as well as jet molded and extrusion formed articles.

The following are examples of phenolic blends of this invention and the cured resins formed therefrom.

Example lUnmodified phenolics (unfilled) Control samples were prepared by mixing 400 g. of an unmodified novolak with a molecular weight (M of 839 and a hexamethylene tetramine content of 9.3 percent and a melting point of 102108 C., with 100 g. CaO in a Waring Blendor for two one-minute periods at a speed of 17,000 rpm. An 8% by 8%" x /s frame mold was then charged with 260 g. of this blend and a plaque was compression molded for /2 hour at 171 C. i5.5 and 1800 p.s.i.:lO percent. ASTM D638 specimens, Type 1, were cut from this plaque.

Samples were also prepared using a mix of 360 g. of the above-described novolak, 90 g. of CaO and 50 g. of one of the following:

(C-l) CaCO (comparative sample) (C-2) Calcium valerate (comparative sample) (C-3) Calcium hexanoate (comparative sample) (C-4) Sebacic acid (comparative sample) (la) Calcium sebacate lb) Calcium isophthalate (1c) Calcium terephthalate (1d) Barium sebacate (1e) Zinc sebacate (lf) Calcium azelate 4 The tensile strength of all samples was tested according to ASTM D-638, before and after heat aging for 24 hours in a forced air oven at 285 C15". The test results are summarized in Table I.

TABLE I21 After 24 hours 285 C. Original percent of Percent of Sample P.s.i. Control P.s.i. control Control 9, 300 100 2, 000 100 (C 1) CaC O 9, 200 99 900 (C 2) Ca Valerate- ,600 800 40 60 200 10 700 35 05 5, 000 295 133 7, 800 300 102 a, 200 160 102 .5, 600 180 68 3, 400 170 ()0 4, 200 210 (lg) Following the procedure of Example 1a, other samples were prepared in which the amount of calcium sebacate was varied from 25 g.-l00 g. (5%20%) with corresponding variations in the amount of novolak. The original tensile strength of the samples varied from 78%95% of the control but the tensile strength after 24 hours at 285 C. varied from 230%310% of the control sample (without the calcium sebacate). Amounts above about 20% calcium sebacate gave no advantage in strength.

(1h) 80 parts of a novolak resin of 740 molecular weight, 10 parts of the barium salt of a meta-benzene-disulfonic acid and 10 parts of hexamethylene tetramine were intimately mixed and ground to pass through a mesh sieve. The sieved material was pressed into a test plaque at 166 C./l000 p.s.i. for 1 hour followed by a post cure at to C. for 6 hours. After curing the test piece was reground, screened through a 60 mesh sieve and its weight loss characteristics in air compared with a control test piece, not containing the barium salt, treated in the same manner. The percentage weight losses of the unmodified versus the modified novolak resins are shown in Table Ib.

1 Calculated on organic portion.

Example 2Unmodified phenolics (asbestos filled) (a) Control samples were prepared by blending 300 g. short fiber asbestos, (Quebec Asbestos Mining Association 6D20), 560 g. unmodified novolak having a fi of 839, a melting point of l02l08 C. and a hexamethylene tetramine content of 9.3 percent, and 140 g. CaO in a sigma arm mixer operating at a speed of 35.6/ 59.6 rpm. for one hour. ASTM D-638 test specimens, Type 1, 42" thick, were compression molded for /2 hour at 171 C.:5.5 and 1800 p.s.i.:lO percent.

(b) Using the same procedure, novolak and asbestos test specimens were prepared from the following compositions: 300 g. short fiber asbestos, 480 g. of the above-described novolak, 120 g. CaO and 100 g. calcium sebacate.

The tensile strength of Examples 2(a) and 2(b) specimens were tested according to AST M D-638, before and after heat aging for six and for 24 hours in a forced air oven at 285 C.i. The test results are summarized in Table II.

Example 3-Unmodified phenolics (asbestos filled) The procedure of Examples 2(a) and 2(b) was followed except that long fiber asbestos (Quebec Asbestos Mining Association 3|R-12) was substituted for the short fiber asbestos. Substantially the same results are obtained as in 2(b) at both percent and 5 percent calcium sebac'ate levels.

Example 4Unmodified phenolics (grit-filled) (a) Control samples were prepared by mixing 880 g. A1 0 abrasive grain having an average grain size of 2.05 mm. with 30 g. of an NaOH catalyzed resole having a formaldehyde2phenol ratio of 0.5 and a viscosity of 10002000 c.p.s. This mix was then blended with 90 g. of an unmodified novolak having an fi of 765, a melting point of 95100 C. and a hexamethylene tetramine content of 9.0 percent. Dog-bone shaped test specimens having a minimum cross section of 1 x /2" were cold pressed to a structure having 19.3 percent by volume voids. These test samples were cured in a forced air oven for 8 hours at programmed temperatures which reached a peak of 180 C.

(b) Using the same abrasive grain and phenolic resins, samples were prepared in which 9 g. of the novolak was substtuited by 9 g. calcium sebacate.

The tensile strength of the samples was tested at 24 and 260 C. Additional samples were heated to 300 C. for /2 hour prior to testing at 24 and 260 C. Other samples were boiled in H O for 24 hours or soaked in H O for 7 days prior to testing. The test results are summarized in Table III.

TABLE III.-TENSILE STRENGTH, P.S.I.

were molded and test specimens prepared as described above. The test results are summarized in Table IV.

TABLE IV Tensile strength after heat aging for 24 hours at 200 0.

Comparable results are obtained by substituting the barium or calcium salt of meta-benzene sulfonic acid for the dicarboxylic acid salts employed in Examples 1 to 5.

(B) Amino-formaldehyde polymers According to this invention a polymer composition is provided by curing a mixture comprising an amino-formaldehyde fusible resin, e.g., melamine-formaldehyde, urea formaldehyde, thiourea-formaldehyde and anilineformaldehyde resins and mixtures thereof, and from about 2 percent to 25 percent of the weight of the amino-formaldehyde compound of a divalent metal salt of a dibasic organic acid as described above.

The amino-formaldehyde prepolymers preferred for the polymerizable compositions of this invention are the melamine formaldehyde prepolymers especially those wherein the ratio of melamine to formaldehyde is about 1:2 to 1:3, particularly the novolaks. The most useful are those classified in the trade as compression or transfer molding grades melamine-formaldehyde compounds.

Amino-formaldehyde polymers are for the most part employed in conjunction with a carbohydrate filler, e.g., wood or walnut-shell flour, preferably alpha-cellulose, paper, rayon or cotton in woven or non-woven form, to form laminates and castings. Generally they are available as the monomer or low-stage resins or prepolymers. Althrough the aniline-formaldehyde compounds produce thermoplastic resins, they are useful in many of the same areas of applications as the thermosetting urea, thiourea and melamine resins.

The novel amino-formaldehyde polymerizable compositions, especially the urea and melamine compositions, are useful or forming laminates, e.g., by dipping sheets hour post cure at 300 0.

Example 5-Phenolic laminates (a) Seven mil kraft paper was impregnated with 21 NaOH catalyzed resole having a formaldehyde: phenol ratio of 1:2, a viscosity of 600 cps. and a solid content of 70 percent, at a weight ratio of paper to resin (solids) of 1:1. The paper was impregnated with the resole mix by immersing the paper in the mix for 1 to 3 minutes. The wet paper was then squeezed through a slit to obtain the desired pick-up. The impregnated paper was then predried at room temperature for 2 hours. Drying was completed in circulating air at 93 C. for 5 minutes.

The impregnated paper was cut into 9" x 9" squares. Twelve of these squares were used to form a laminate with the sheets alternating perpendicularly with respect to ma. chining direction. The laminate was molded bet-ween chromium plated metal plaques for /2 hour at 164 C.:3 and 1000 p.s.i. The sheets were then cooled to room temperature in 5 minutes under pressure.

(b) Other sheets of the 7 mil kraft paper were impregnated with a dispersion formed by blending 1 kg. of the above-described resole with 78 g. of calcium isophthalate in a paint mill, at the same 1:1 weight ratio. The laminates or fabric in the polymerizable solution containing a polymerization catalyst removing the excess, drying under controlled conditions to partially set the resin and laminating a multiplicity of layers under heat and high pressure.

They are also useful to form molded articles, using about 25-50 percent of a flour or cellulosic material as a filler, and the usual methods of molding these thermosetting plastics in the absence of the organometallic salt. If the molding composition is supplied as pills or tablets, the organometallic salt is preferably thoroughly blended with the amino-formaldehyde compound before the formation of the pills or tablets.

The polymerizable compositions of this invention are also useful in producing foams which are of particular value, e.g., as insulation, because of improved tensile and flexural strength. For example, a water soluble ureaformaldehyde resin containing 2 to 25 percent by weight of a divalent metal salt of an organic acid, calculated on the weight of the urea-formaldehyde compound, and wood flour or other filler, beaten into a foam and cured by addition of suitable catalysts and dried, bakes foams both above and below 0.05 density of greater strength and resistance to cracking than the corresponding foams in which the salts are omitted.

The following illustrates the amino-formaldehyde blends of this invention and their use.

Example 6.Melamine-formaldehyde blends (a) 225 g. of an alpha-cellulose-containing melamineformaldehyde molding compound having a density of 1.5 (Cymel 1077, American Cyanamide) was homogenized with 25 g. calcium terephthalate on a hammer mill. A chromium plated steel mold of the size 8 /2" X 8 /2 X /8" was charged with the mix and the molding was carried out at 167 C. and 2000 p.s.i. pressure over a period of 3 minutes allowing a pump-breath after the first minute. The plaque was ejected after cooling down to 49 C. Test specimens for the determination of the tensile strength (ASTM D638, Type 1), flexural strength (ASTM D-790), and deflection temperature (ASTM D-640) were prepared and tested.

Using the same procedure, test specimens were also prepared from compositions in which the calcium terephthalate was replaced by the same amount of calcium isophthalate, azelate or sebacate or the salt was omitted as a control.

The test results are summarized in the following Table V.

Comparable results are obtained by substituting an equivalent amount of calcium phthalate or calcium or barium metabenzene disulfonic acid for the dibasic acid salts employed in Examples 6(a) to 6(d).

(C) POLYESTERS According to this invention, a polymerizable composition is provided comprising a polyester prepolymer containing ethylenic unsaturation and from about 2 to about 25 percent by weight of the prepolymer of a divalent metal salt of a dibasic organic acid as described above.

The polyester prepolymers employed in the polymerizable compositions of this invention are the unsaturated ester class of casting and low-pressure laminating resins, i.e., polyester prepolymers having unsaturated ethylenic groups. These polyesters polymerize through carbon to carbon bonding to form cross-linked thermosetting structures. They are generally prepared by the use of an unsaturated dior polybasic acid, e.g., maleic acid, or an unsaturated alcohol, e.g., allyl alcohol or both, as a portion of the esterification mixture. Another unsaturated compound, e.g., up to 50 percent styrene, can be included in the prepolymer mixture to form a copolymer, along with the halogenated and antimony compounds conventionally included in such prepolymer mixtures.

These polyesters are preferably condensation products of dior polyols and dior polycarboxylic acids, e.g., the polyester formed by the esterification of aliphatic glycols, e.g., ethylene glycol, propylene glycol, a polyethylene ether glycol, etc., with an aliphatic or aromatic dicarboxylic acid or mixture thereof which provides the ethylenic unsaturation in the acid moiety, e.g., a mixture of phthalic and maleic anhydrides. As stated above, the mixture can include other polymerizable monomers or polymers containing ethylenic unsaturation, e.g., styrene, to copolymerize with the unsaturated groups in the polyester and modify the properties of the polyester. As used to prepare thermosetting resins, they are generally viscous liquid prepolymers or contact resins which, when mixed with an appropriate catalyst, usually a peroxide catalyst, spontaneously set to a hard resin. For further description of this class of materials, see US. Pats. 2,370,565; 2,370,566; 2,370,572; 2,370,573; 2,370,574; 2,370,578; 2,384,115 to 2,384,125. These polyester forming mixtures are conventionally employed in conjunction witha fibrous material, eg., spun glass filaments or fabric to form large articles and self-supporting structures. See US. Pats. 2,276,004; 2,337,007; 2,342,988; 2,392,108; 2,392,707; 2,394,730.

Polyesters are a relatively expensive class of resins. Their widespread use is therefore a tribute to their versatility. It is highly desirable to employ inexpensive fillers or extenders to reduce their cost. However, it is difficult to provide extenders which retain the desired qualities of polyester resin.

It has now been found that divalent metal salts of the dibasic organic acids described above act as extenders for polyesters which not only retain their desirable properties but often these properties are enhanced, particularly their tensile strength, which is a highly unexpected result.

The divalent salt is employed in an amount between about 2 and 25 percent, preferably within the range of about 5 to 10 percent. The selected salt, preferably calcium phthalate, and the selected polyester prepolymer, preferably a styrene modified liquid polyester prepolymer, are thoroughly mixed prior to catalyzed curing or polymerization. Conventional casting, molding and polymerization techniques can be employed.

The following is illustrative of the polyester blends of this invention.

Example 7Polyester blends (a) 300 g. of a styrene-modified general purpose (ethylene glycol-phthalic and maleic anhydride) polyester having a viscosity of 2700 cps./ 25 C. (Brookfield) was catalyzed with 5.6 ml. of a 60 percent solution of methylethyl ketone peroxide in dibutyl phthalate. 30 g. calcium adipate was added and the mass was thoroughly mixed. This mix was cast into an 8" x 8" x A" glass mold and cured in a water bath at 50 C. for 17 hours. A rigid polyester sheet was obtained. This sheet was postcured at C. for 24 hours. Test specimens (according to ASTM D-638, size No. 1) were cut.

Using the same procedure, test specimens were also prepared employing the same polyester resin and catalyst in the same amounts but substituting 30 g. calcium terephthalate for the calcium adipate or omitting the salt completely as a control.

The tensile strength of these specimens was tested according to ASTM D-638. The test results are shown in Table VI.

Comparable results are obtained by substituting an equivalent weight of calcium phthalate or sebacate or calcium or barium meta-benzene disulfonic acid for the dibasic acid salt employed in Examples 7(a) and 7(b).

(D) POLYSTYRENES According to this invention, there is provided mixtures of polystyrene and from about 2 to about 25 percent by weight thereof of a divalent metal salt of a dibasic organic acid as described above. These mixtures can be formed into shaped articles of manufacture having improved tensile strength, either before or after heat aging,

compared with the identical shaped article formed entirely of the selected polystyrene.

The shaped article of manufacture can be formed by extrusion, molding, machining, casting to form sheets or oriented films, foam casting or molding, e.g., to form oriented foamed sheets by balloon extrusion. The conventional styrene polymerization techniques can be used to form the polystyrene. Although the compositions of this invention are ordinarily produced by blending the selected polystyrene With the selected organometallic salt, they can also be formed by polymerization of styrene in the presence of the organometallic salt, e.g., by batch mass, solution of emulsion or suspension polymerization or continuous mass polymerization in which the styrene monomer and organometallic salt are thoroughly mixed before or during polymerization.

When polystyrene is employed, a heat resistant grade, e.g., a high purity homopolymer or a copolymer formed with up to about 35 percene vinyltoluene, is preferred. These are referred to in the trade as injection molding or extrusion grade.

Contrary to the results obtained with most fillers, the organometallic salts employed in these compositions do not adversely affect heat distortion temperature. Sunlight yellowing is often reduced and critical elongation as well as tensile strength is improved. Inert fibrous fillers, e.g., glass filament or fibers or asbestos fibers are desirably incorporated into the shaped articles of manufacture.

The following is illustrative of the polystyrene blends of this invention.

Example 8Polystyrene blends (a) 190 g. of a heat resistant polystyrene with a melt flow of 1.04 g. per 10 minutes (ASTM D-1238, condition G) and a density of 1.06 (Dylene 9) was milled with 10 g. calcium isophthalate on a two roll mill for minutes. The front and back roll were kept at 167 C. The mix was compression molded at 177 C. and 3000 psi, using a 6 x 6" x mold. Test specimens were cut and the tensile strength of these specimens was tested, according to ASTM D-638, in which samples are tested, before and after heat aging in a forced air oven.

Samples 8(b) (2 percent calcium isophthalate) and 8(c) (no calcium isophthalate) were prepared and tested using the same procedure.

The results are given in the following Table VIII.

TABLE VII Tensile strength After heat aging Initial 48 hours at 195 F.

Percent Percent of of Samples I.s.i control I.s.i. control 8(a) 5% Ca isophthalate 6, 360 134 6,000 119 8(b) 2% Ca isophthalate 4, 870 103 5, 650 112 8(0) control 4, 750 100 5, 050 100 Comparable results are obtained by substituting an equivalent amount of calcium phthalate or sebacate or calcium or barium meta-benzenedisulfonic acid for the calcium isophthalate employed in Examples 8(a) and 8(b).

(E) ACRYLATES The polyacrylates employed in this invention are the thermoplastic polymers of esters of acrylic acid and methacrylic acid, preferably the lower-alkyl esters of 1-4 car bon atoms and preferably the methyl ester, and mixtures or copolymers thereof. Polymethyl methacrylate and polymethyl acrylate are the polymers of choice.

The compositions of this invention are generally formed by blending the selected organometallic salt with the melted polyacrylate until a uniform mixture is obtained, e.g., by hot milling. The compositions are generally substantially free from other organic polymeric materials. How ever, when a calcium phthalate is employed, a copolymer of methylmethacrylate and, e.g., 1040 percent of styrene of acrylonitrile can be used with improved results. Con ventional fillers and reinforcing fibrous materials can also be incorporated in the compositions.

The following illustrates the polyacrylate blends of this invention.

Example 9Polymethyl methacrylate blends (a) 142.5 g. of a heat resistant polymethyl methacrylate with a density of 1.19 and a refractive index of 1.49 (Rohm & Haas Plexiglas V) was milled on a two roll mill with 7.5 g. calcium isophthalate (5 percent) at 177 C. for 5 minutes. The blend was molded in a 6" x 6" x mold at 177 C. and 4000 psi. pressure.

Test specimens were cut and the tensile strength of these specimens was tested, according to ASTM D-638, in which samples were tested before and after heat aging (48 hours at C. in a forced air oven).

Samples 9(b) and 9(c) were made using the same procedure but employing lesser amounts of calcium isophthalate. In sample 9(d) calcium terephthalate was substituted. Sample 9(c) was the control with no acid salt. The test results are summarized in the following Table VIII.

Comparable results are obtained by substituting an equivalent weight of calcium phthalate or sebaeate or barium meta-benzenedisulfonic acid for the dibasic acid salts employed in Example 9(a)-9 (d).

(F) CELLULOSE DERIVATIVES According to this invention, cellulose derivative mixtures are provided comprising a thermoplastic ether or ester of cellulose and from about 2 to about 25 percent of a divalent metal salt of a dibasic organic acid as described above. These compositions, especially when formed into shaped articles of manufacture such as sheets, films, filaments, etc., have superior elongation than the corresponding cellulose derivative in the absence of the organometallic salt. The improvement is particularly noticeable after exposure to elevated temperatures. They thus have improved utility in the areas of use for cellulose derivatives, e.g., films, sizing materials, etc. where good elongation is desired.

The cellulose ethers include the aliphatic ethers, e.g., the water soluble methyl, ethyl, u-hydroxypropyl, hydroxyethyl, carboxymethyl and carboxyethyl ethers, and the organic solvent soluble ethers, e.g., propyl, butyl, amyl ethers and mixed ethers, e.g., methyl hydroxypropylcellulose.

The cellulose esters include the aliphatic, aryl, and inorganic esters, e.g., cellulose acetate, cellulose propionate,

1 l cellulose butyrate, sodium cellulose sulfate, nitrocellulose, sodium cellulose phosphate, mixed esters, e.g., cellulose acetate butyrate, cellulose acetate propionate, of conven tional degrees of substitution. Preferred derivatives are cellulose acetate and ethyl cellulose.

For the most part, the cellulose blends of this invention contain only a cellulose derivative or derivatives as the polymeric component. They can, however, include the conventional stabilizers, lubricants, etc. They are ordinarily formed by hot milling a melt of the selected cellulose derivative and the selected organometallic salt. However, they can also be formed from solution or suspension.

The following illustrates the cellulose derivative blends of this invention.

Example 10Ethyl cellulose blends (a) 180 g. ethyl cellulose with a density of 1.11 and a flow grade (ASTM D-569) of M-MH (Ethocel 890) was milled with 20 g. calcium isophthalate on a two roll mill for 8 minutes. The front roll temperature was kept at 143 C. and the back roll temperature at 93 C.

A 6" x 6" x A mold was charged with 100 g. of the blend and the molding was carried at 177 C. and 4000 p.s.i. pressure.

Samples 10(b)10(f) were made using the same procedure but employing varying amounts of calcium isophthalate, or lead isophthalate, barium sebacate or omitting the organic salt as a control.

Test specimens were cut and the tensile strength of these specimens was tested, according to ASTM D-638, ing which samples were tested before and after heat aging (48 hours at 105 C. in a forced air oven). The test results are summarized in the following Table IX.

Example l1-Cellulose acetate blends (a) 160 g. of a cellulose acetate with a density of 1.29 with a flow temperature of 338 F. (ASTM D-569) was milled with 40 g. calcium isophthalate on a two roll mill for minutes. The front roll temperature was kept at 160 C. and the back roll temperature at 155 C.

A 6" x 6" X mold was charged with 100 g. of the blend. A plaque was molded at 182 C. and 4000 p.i.a. pressure. Samples (b)(h) were prepared using the same 12 procedure but varying the amount of calcium isophthalate, substituting barium sebacate or zinc sebacate or omitting the salt for a control. The yield strength of these blends is shown in the following Table X.

The 20 percent calcium isophthalate had notably superior yield strength after heat aging at 93 C. and 84 hours.

Comparable results are obtained by substituting an equivalent weight of calcium phthalate or calcium or barium metalbenzene disulfonic acid for the dibasic acid salts employed in Examples 10(a)10(e) and 11(a) (g)- We claim:

1. An amino-formaldehyde polymerizable composition consisting essentially of a solid aminoformaldehyde prepolymer and from about 2 percent to about 25 percent of the total weight of said prepolymer of a divalent metal salt of a dibasic organic acid selected from the group consisting of saturated alkanedioic acids, aromatic carboxylic dicarboxylic acids, and aromatic carbocyclic disulfonic acids.

2. A composition according to claim 1 wherein the prepolymer is a melamine-formaldehyde compound.

3. A composition according to claim 2 wherein the salt is a Group 11 metal salt of a carbocyclic aromatic dicarboxylic acid.

4. A composition according to claim 3 wherein the acid is a phthalic acid.

5. A composition according to claim 3 wherein the metal salt is a calcium salt.

6. A composition according to claim 3 wherein the salt is a calcium phthalate.

References Cited UNITED STATES PATENTS 3,135,709 6/1964 Luneburg et al 26021 WILLIAM H. SHORT, Primary Examiner R. J. KOCH, Assistant Examiner US. Cl. X.R. 

